# Capacitor in Voltmeter

#### MartinV

Joined Jun 2, 2011
22
I am not sure this is for the homework section, but I hope I'm not way off
So here's the thing: I have this circuit (where you can notice it's a highly sensitive voltmeter for small voltages (micro values and similar)), I am not sure that I got it right. The voltage at U2 will get negative at the moment the switch P1 closes because of the left "plate" of the capacitor (that used to be the one of higher potential) which goes to 0 (because of the ground) and the right one (of lower potential) goes to -Up(previous voltage witch switch opened).
Am I on the right track here?
The entire circuit (picture taken with a mobile phone, so sorry for the low quality):

#### bertus

Joined Apr 5, 2008
20,102
Hello,

It looks like a chopper stabelized amplifier circuit.
To avoid offsets the signal is chopped.
To smoothen the signal before the meter, there is a lowpass filter made by Rf and Cf.

Bertus